16-Bit/18-Bit, 16 ؋ FS
PCM Audio DACs
110 dB SNR
Fast Settling Permits 16؋ Oversampling
؎3 V Output
Optional Trim Allows Super-Linear Performance
؎5 V Operation
16-Pin Plastic DIP and SOIC Packages
Pin-Compatible with AD1856 & AD1860 Audio DACs
2s Complement, Serial Input
High-End Compact Disc Players
Digital Audio Amplifiers
DAT Recorders and Players
Synthesizers and Keyboards
The AD1851/AD1861 is a monolithic PCM audio DAC. The
AD1851 is a 16-bit device, while the AD1861 is an 18-bit de-
vice. Each device provides a voltage output amplifier, DAC,
serial-to-parallel register and voltage reference. The digital por-
tion of the AD1851/AD1861 is fabricated with CMOS logic
elements that are provided by Analog Devices’ 2 µm ABCMOS
process. The analog portion of the AD1851/AD1861 is fabri-
cated with bipolar and MOS devices as well as thin-film
This combination of circuit elements, as well as careful design
and layout techniques, results in high performance audio play-
back. Laser-trimming of the linearity error affords low total har-
monic distortion. An optional linearity trim pin is provided to
allow residual differential linearity error at midscale to be elimi-
nated. This feature is particularly valuable for low distortion
reproductions of low amplitude signals. Output glitch is also
small, contributing to the overall high level of performance. The
output amplifier achieves fast settling and high slew rates, pro-
viding a full ± 3 V signal at load currents up to 8 mA. When
used in current output mode, the AD1851/AD1861 provides a
± 1 mA output signal. The output amplifier is short circuit
protected and can withstand indefinite shorts to ground.
The serial input interface consists of the clock, data and latch
enable pins. The serial 2s complement data word is clocked into
the DAC, MSB first, by the external clock. The latch enable
signal transfers the input word from the internal serial input
register to the parallel DAC input register. The AD1851 input
clock can support a 12.5 MHz data rate, while the AD1861 in-
put clock can support a 13.5 MHz data rate. This serial input
port is compatible with second generation digital filter chips
used in consumer audio products. These filters operate at over-
sampling rates of 2ϫ, 4ϫ, 8ϫ and 16ϫ sampling frequencies.
FUNCTIONAL BLOCK DIAGRAM
NC = NO CONNECT
14 MSB ADJ
The critical specifications of THD+N and signal-to-noise ratio
are 100% tested for all devices.
The AD1851/AD1861 operates with ± 5 V power supplies, mak-
ing it suitable for home use markets. The digital supply, VL, can
be separated from the analog supplies, VS and –VS, for reduced
digital crosstalk. Separate analog and digital ground pins are
also provided. Power dissipation is 100 mW typical.
The AD1851/AD1861 is available in either a 16-pin plastic DIP
or a 16-pin plastic SOIC package. Both packages incorporate
the industry standard pinout found on the AD1856 and
AD1860 PCM audio DACs. As a result, the AD1851/AD1861
is a drop-in replacement for designs where ± 5 V supplies have
been used with the AD1856/AD1860. Operation is guaranteed
over the temperature range of –25°C to +70°C and over the
voltage supply range of ± 4.75 V to ± 5.25 V.
l. AD1851 16-bit resolution provides 96 dB dynamic range.
AD1861 18-bit resolution provides 108 dB dynamic range.
2. No external components are required.
3. Operates with ± 5 V supplies.
4. Space saving 16-pin SOIC and plastic DIP packages.
5. 100 mW power dissipation.
6. High input clock data rates and 1.5 µs settling time permits
2ϫ, 4ϫ, 8ϫ and 16ϫ oversampling.
7. ± 3 V or ± 1 mA output capability.
8. THD + Noise and SNR are 100% tested.
9. Pin-compatible with AD1856 & AD1860 PCM audio DACs.
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.